A little change in your present query
$Query = "CREATE table $TableName (id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY, title TEXT, category TEXT, ad_descriptions TEXT, ad_closed TEXT, ad_price TEXT, posted_On INT(20), zip TEXT, campus TEXT)";
Try this query it will work.
and if you want to customize more your timestamp and date.
Than see date() and mktime() from php manual.
If face any problem pls let me know.
Thanks